When we give reasons for accepting a claim, we are making an argument.
The reasons we give are called the premises of the argument, and
the claim they allegedly support is called the conclusion. If the
premises are acceptable, and if they adequately support the conclusion,
then our argument is a good one. If not -- the premises are dubious, or
if they do not justify the conclusion -- then our argument is fallacious.
A fallacious argument is a bogus one, for it fails to do what it purports
to do, namely, provide a good reason for accepting a claim. Unfortunately,
logically fallacious arguments can be psychologically compelling. Since
most people have never learned the difference between a good argument and
a fallacious one, they are often persuaded to believe things for no good
reason. To avoid holding irrational beliefs, then, it is important to understand
the many ways in which an argument can fail.

An argument is fallacious if it contains (1) unacceptable premises,
(2) irrelevant premises, or (3) insufficient premises. Premises are unacceptable
if they are at least as dubious as the claim they are supposed to support.
In a good argument, you see, the premises provide a firm basis for accepting
the conclusion. If the premises are shaky, the argument is inconclusive.
Premises are irrelevant if they have no bearing on the truth of
the conclusion. In a good argument, the conclusion follows from the premises.
If the premises are logically unrelated to the conclusion, they provide
no reason to accept it. Premises are insufficient if they do not
establish the conclusion beyond a reasonable doubt. In a good argument,
the premises eliminate reasonable grounds for doubt. If they fail to do
this, they don't justify the conclusion.

So when someone gives you an argument, you should ask yourself: Are
the premises acceptable? Are they relevant? Are they sufficient? If the
answer to any of these questions is no, then the argument is not logically
compelling.

Unacceptable Premises

Begging the Question

An argument begs the question -- or argues in a circle -- when its conclusion
is used as one of its premises. For example, some claim that one should
believe that God exists because the Bible says so. But when asked why we
should believe the Bible, they answer that we should believe it because
God wrote it. Such people are begging the question, for they are assuming
what they are trying to prove, namely that God exists. Here's another example:
"Jane has telepathy," says Susan. "How do you know?"
asks Jill. "Because she can read my mind," replies Susan. Since
telepathy is, by definition, the ability to read someone's mind, all Susan
has told us is that she believes that Jane can read her mind because she
believes that Jane can read her mind. Her reason merely reiterates her
claim in different words. Her reason provides no additional justification
for her claim.

False Dilemma

An argument proposes a false dilemma when it presumes that only two
alternatives exist when in actuality there are more than two. For example,
"Either science can explain how she was cured or it was a miracle.
Science can't explain how she was cured. So it must be a miracle."
These two alternatives do not exhaust all the possibilities. It's possible,
for example, that she was cured by some natural cause that scientists don't
yet understand. Because the argument doesn't take this possibility into
account, it's fallacious. Again: "Either have your horoscope charted
by an astrologer or continue to stumble through life without knowing where
you're going. You certainly don't want to continue your wayward ways. So
you should have your horoscope charted by an astrologer." If someone
is concerned about the direction her life is taking, there are other things
she can do about it than consult an astrologer. Since there are other options,
the argument ins fallacious.

Irrelevant Premises

Equivocation

Equivocation occurs when a word is used in two different senses in an
argument. For example, consider this argument: "(i) Only man is rational.
(ii) No woman is a man. (iii) Therefore no woman is rational." The
word man is used in two different ways here: in the first premise
it means human being but in the second it means male. As a result, the
conclusion doesn't follow the premises. Here's another example: "It's
the duty of the press to publish news that's in the public interest. There
is a great public interest in UFOs. Therefore the press fails in its duty
if it does not publish articles on UFOs." In the first premise, the
phrase public interest means the public welfare, but in the second,
it means what the public is interested in. The switch in meaning invalidates
the argument.

Composition

An argument may claim that what is true of the parts is also true of
the whole; this is the fallacy of composition. For example, consider this
argument: "Subatomic particles are lifeless. Therefore anything made
of them is lifeless." This argument is fallacious because a whole
may be greater than the sum of its parts; that is, it may have properties
not possessed by its parts. A property had by a whole but not by its parts
is called an emergent property. Wetness, for example, is an emergent
property. No individual water molecule is wet, but get enough of them together
and wetness emerges.

Just as what's true of the part may not be true of the whole, what's
true of a member of a group may not be true of the group itself. For example,
"Belief in the supernatural makes Joe happy. Therefore, universal
belief in the supernatural would make the nation happy." This doesn't
follow because everybody's believing in the supernatural could have effects
quite different from one person's believing in it. Not all arguments from
part to whole are fallacious, for there are properties that the parts and
wholes share. The fallacy lies in assuming that what's true of the
parts is true of the whole.

Division

The fallacy of division is the converse of the fallacy of composition.
It occurs when one assumes that what is true of the whole is also true
of its parts. For example: "We are alive and we are made of subatomic
particles. So they must be alive too." To argue this way is to ignore
the very real difference between parts and wholes. Here's another example:
"Society's interest in the occult is growing. Therefore Joe's interest
in the occult is growing." Since groups can have properties that are
not had by their members, such an argument is fallacious.

Appeal to the Person

When someone tries to rebut an argument by criticizing or denigrating
its presenter rather than by dealing with the argument itself, that person
is guilty of the fallacy of appealing to the person. This fallacy is called
ad hominem, or "to the man." For example, "This theory
has been proposed by a believer in the occult. Why should we take it seriously?"
Or: "You can't believe Dr. Jones's claim that there is no evidence
for life after death. After all, he's an Atheist." The flaw in these
arguments is obvious; an argument stands or falls on its own merit; who
proposes it is irrelevant to its soundness. Crazy people can come up with
perfectly sound arguments, and sane people can talk nonsense.

Genetic Fallacy

To argue that a claim is true or false on the basis of its origin is
to commit the genetic fallacy. For example: "Jones's idea is the result
of a mystical experience, so it must be false (or true)." Or: "Jane
got that message from a Ouija board, so it must be false (or true)."
These arguments are fallacious because the origin of a claim is irrelevant
to its truth or falsity. Some of our greatest advances have originated
in unusual ways. For example, the chemist August Kekulé discovered
the benzine ring while staring at a fire and seeing the image of a serpent
biting its tail. The theory of evolution came to British naturalist Alfred
Russell Wallace while in a delirium. Archimedes supposedly arrived at the
principle of displacement while taking a bath, from which he leapt shouting,
"Eureka!" The truth or falsity of an idea is determined not by
where it came from, but by the evidence supporting it.

Appeal to Authority

We often try to support views by citing experts. This appeal to authority
is perfectly valid -- provided that the person cited really is an expert
in the field in question. If not, it is fallacious. Celebrity endorsements,
for example, often involve fallacious appeals to authority because being
famous doesn't necessarily give you any special expertise. The fact that
Dionne Warwick is a great singer, for example, doesn't make her an expert
on the efficacy of psychic hot lines. Similarly, the fact that Linus Pauling
is a Nobel Prize winner doesn't make him an expert on the efficacy of vitamin
C. Pauling claimed that taking massive doses of vitamin C would help prevent
colds and increase the life expectancy of people suffering from cancer.
That may be the case, but the fact that he said it doesn't justify our
believing it. Only rigorous clinical studies confirming these claims can
do that.

Appeal to the Masses

A remarkably common but fallacious form of reasoning is: "It must
be true (or good) because everybody believes (or does) it." Mothers
understand this as a fallacy; they often counter this argument by asking:
"If everyone jumped off a cliff, would you do it too?" Of course
you wouldn't. What this shows is that just because a lot of people believe
something or like something doesn't mean that it is true or good. A lot
of people used to believe that the Earth was flat, but that certainly didn't
make it so. Similarly, a lot of people used to believe that women should
not have the right to vote. Popularity is not a reliable indication either
of reality or of value.

Appeal to Tradition

We appeal to tradition when we argue something must be true (or good)
because it is part of an established tradition. For example: "Astrology
has been around for ages, so there must be something to it." Or: "Mothers
have always used chicken soup to fight colds, so it must be good for you."
These arguments are fallacious because traditions can be wrong. This becomes
obvious when you consider that slavery was once an established tradition.
The fact that people have always done or believed something is no reason
for believing that we should continue to do or believe something.

Appeal to Ignorance

The appeal to ignorance comes in two varieties: using an opponent's
inability to disprove a conclusion as proof of the conclusion's correctness,
and using an opponent's inability to prove a conclusion as proof of its
incorrectness. In the first case, the claim is that since there is not
proof that something is true, it must be false. For example: "There
is no proof that the parapsychology experiments were fraudulent, so I'm
sure they weren't." In the second case, the claim is that since there
is no proof that something is false, it must be true. For Example: "Bigfoot
must exist because no one has been able to prove that he doesn't."
The problem with these arguments is that they take a lack of evidence for
one thing to be good evidence for another. A lack of evidence, however,
proves nothing. In logic, as in life, you can't get something for nothing.

Appeal to Fear

To use the threat of harm to advance one's position is to commit the
fallacy of the appeal to fear. It is also known as swinging the big stick.
For example: "If you do not convict this criminal, one of you may
be her next victim." This is fallacious because what a defendant might
do in the future is irrelevant to determining whether she is responsible
for a crime committed in the past. Or: "You should believe in God
because if you don't you'll go to hell." Such an argument is fallacious
because it gives us no reason for believing that God exists. Threats extort;
they do not help us arrive at the truth.

Insufficient Premises

Hasty Generalization

You are guilty of hasty generalization, or jumping to conclusions, when
you draw a general conclusion about all things of a certain type on the
basis of evidence concerning only a few things of that type. For example:
"Every medium that's been investigated has turned out to be a fraud.
You can't trust any of them." Or: "I know one of those psychics.
They're all a bunch of phonies." You can't make a valid generalization
about an entire class of things from observing only one -- or even a number
of them. An inference from a sample of a group to the whole group is legitimate
only if the sample is sufficiently large and every member of the group
has an equal chance to be in the sample.

Faulty Analogy

An argument from analogy claims that things which resemble one another
in certain respects resemble one another in further respects. For example:
"The Earth has air, water, and living organisms. Mars has air and
water. Therefore Mars has living organisms." The success of such arguments
depends upon the nature and extent of the similarities between the two
objects. The greater their dissimilarities, the less convincing the argument
will be. For example, consider this argument: "Astronauts wear helmets
and fly in spaceships. The figure in this Mayan carving seems to be wearing
a helmet and flying in a spaceship. Therefore it is a carving of an ancient
astronaut." Although features of the carving may bear a resemblance
to a helmet and spaceship, they bear a greater resemblance to a ceremonial
mask and fire. The problem is that any two things have some features in
common. Consequently and argument from analogy can be successful only if
the dissimilarities between the things being compared are insignificant.

False Cause

The fallacy of false cause consists of supposing that two events are
causally connected when they are not. People often claim, for example,
that because something occurred after something else it is caused by it.
Latin scholars dubbed this the fallacy of post hoc, ergo propter hoc,
which means, "After this, therefore because of this." Such reasoning
is fallacious because from the fact that two events are constantly conjoined,
it doesn't follow that they are causally related. Night follows day, but
that doesn't mean that day causes night. Suppose that ever since you wore
crystals around your neck you haven't caught a cold. From this you can't
conclude that the crystals caused you to stay healthy, because any number
of other factors could be involved. Only if it has been established beyond
a reasonable doubt that other factors were not involved -- through a controlled
study, for example -- can you justifiably claim that there is a causal
connection between the two events.

Our formula for inquiry consists of four steps, which we represent by the
acronym SEARCH. The letters stand for the key words in the four steps

1. State the claim.
2. Examine the Evidence for the claim.
3. Consider Alternative hypotheses.
4. Rate, according to the Criteria of adequacy, each Hypothesis.

The acronym is arbitrary and artificial, but it may help you remember
the formula's vital components. Go through these steps any time you're
faced with an extraordinary claim.

Note that throughout this chapter we use the words hypothesis
and claim interchangeably. We do so because any weird claim, like
any claim about events and entities, can be viewed as a hypothesis -- as
an explanation of a particular phenomenon. Thinking of weird claims as
hypotheses is important because effectively evaluating weird claims involves
essentially the same hypothesis-assessing procedure used in science.

Step 1: State the Claim

Before you can carefully examine a claim, you have to understand what
it is. It's vital to state the claim in terms that are as clear
and as specific as possible. "Ghosts are real" is not
a good candidate for examination because it's vague and nonspecific. A
better claim is "The disembodied spirits of dead persons exist and
are visible to the human eye." Likewise, "Astrology is true"
is not much to go on. Its better to say, "Astrologers can correctly
identify someone's personality traits by using sun signs." Even these
revised claims aren't as unambiguous and definitive as they should be.
(Terms in the claims, for example, could be better defined. What is meant
by "spirit"? What does it mean to "correctly identify someone's
personality traits"?) But many of the extraordinary claims you run
into are of this caliber The point is that before examining any claim,
you must achieve maximum clarity and specificity of what the claim is.

Step 2: Examine the Evidence for the Claim

Ask yourself what reasons there are for accepting the claim. That is,
what empirical evidence or logical arguments are there in the claim's favor?
Answering this question entails taking inventory of both the quantity and
quality of the reasons for believing that the claim is true. An honest
and thorough appraisal of reasons must include:

1. Determining the exact nature and limitations of the empirical
evidence. This means assessing not only what the evidence is but whether
there are any reasonable doubts regarding it. You have to try to find out
if it's subject to any of the deficiencies we've previously discussed --
the distortions of human perception, memory, and judgment; the errors and
biases of scientific research; the difficulties inherent in ambiguous data.
Sometimes even a preliminary survey of the facts may force you to admit
that there really isn't anything mysterious that needs explaining. Or perhaps
investigating a little mystery will lead to a bigger mystery. At any rate,
attempting an objective assessment of the evidence takes courage Many true
believers have never taken this elementary step.

2. Discovering if any of these reasons deserve to be disqualified.
As we've seen, people frequently offer considerations in support of a claim
that should be discounted. These include wishful thinking, faith, unfounded
intuition, and subjective certainty. The problem is that these factors
aren't reasons at all. In themselves, they can't provide any support for
a claim.

3. Deciding whether the hypothesis in question actually explains
the evidence. If it doesn't -- if important factors are left out of
account -- the hypothesis is not a good one. In other words, a good hypothesis
must be relevant to the evidence its intended to explain. If it isn't,
there's no reason to consider it any further.

Step 3: Consider Alternative Hypotheses

It's never enough to consider only the hypothesis in question and its
reasons for acceptance. If you ever hope to discover the truth, you must
also weigh alternative hypotheses and their reasons.

Take this hypothesis, for example Rudolph the Red-Nosed Reindeer
-- Santa's funny, flying, furry headlight -- is real and lives at the North
Pole. As evidence for this hypothesis we could submit these facts: Millions
of people (mostly children) believe Rudolph to be real; his likeness shows
up everywhere during the Christmas holidays; given the multitude of reindeer
in the world and their long history, its likely that at some time a reindeer
with flying capabilities would either evolve or be born with the necessary
mutations; some people say that they have seen Rudolph with their own eyes.
We could go on and on and build a fairly convincing case for the hypothesis
-- soon you may even come to believe that we were on to something.

The hypothesis sounds great by itself, but when considered alongside
an alternative hypothesis -- that Rudolph is a creature of the imagination
created in a Christmas song -- it looks ludicrous. The song hypothesis
is supported by evidence that's overwhelming; it doesn't conflict with
well-established theory in biology (as the real-Rudolph hypothesis
does); and, unlike its competitor, it requires no postulations about new
entities.

This third step involves creativity and maintaining an open mind. It
requires asking whether there are other ways to account for the phenomenon
at hand and, if there are, what reasons there are in favor of these alternative
hypotheses. This step involves applying step two to all competing explanations.

Its also important to remember that, when people are confronted with
some extraordinary phenomenon, they often immediately offer a hypothesis
involving the paranormal or supernatural and then can't imagine a natural
hypothesis to account for the facts. As a result, they assume that the
paranormal or supernatural hypothesis must be right. But this assumption
is unwarranted. Just because you can't think of a natural explanation doesn't
mean there isn't one. It may be (as has often been the case throughout
history) that you're simply unaware of the correct natural explanation.
As pointed out in Chapter 2, the most reasonable response to a mystifying
fact is to keep looking for a natural explanation.

We all have a built-in bias that urges us to latch onto a favorite
hypothesis and ignore or resist all alternatives We may believe that we
needn't look at other explanations since we know that our favorite one
is correct. This tendency may make us happy (at least for a while), but
it's also a good recipe for delusion. We must work to counteract this bias.
Having an open mind means being willing to consider any possibility and
changing your view in light of good reasons.

Step 4: Rate, According to the Criteria
of Adequacy, Each Hypothesis

Now it's time to weigh competing hypotheses and see which are found
wanting and which are worthy of belief. Simply cataloguing the evidence
for each hypothesis isn't enough. We need to consider other factors that
can put that evidence in perspective and help us weigh hypotheses when
there's no evidence at all, which is often the case with weird things.
As discussed in Chapter 8, these potent factors are the criteria of adequacy.
By applying them to each hypothesis, we can often eliminate some hypotheses
right away, give more weight to some than others, and decide between hypotheses
that may at first seem equally strong

1 Testability. Ask Can the hypothesis be tested? Is there any
possible way to determine whether the hypothesis is true or false? Many
hypotheses regarding extraordinary phenomena aren't testable. This doesn't
mean they're false. It means they're worthless. They are merely assertions
that we'll never be able to know. What if we claim that there is an invisible,
undetectable gremlin in your head that sometimes causes you to have headaches.
As an explanation for your headaches, this hypothesis is interesting but
trivial. Since by definition there's no way to determine if this gremlin
really exists, the hypothesis is amazingly uninformative. You can assign
no weight to such a claim.

2. Fruitfulness. Ask Does the hypothesis yield observable, surprising
predictions that explain new phenomena? Any hypothesis that does so gets
extra points. Other things being equal, hypotheses that make accurate,
unexpected predictions are more likely to be true than hypotheses that
don't. (Of course, if they yield no predictions, this in itself doesn't
show that they're false.) Most hypotheses regarding weird things don't
make observable predictions.

3. Scope. Ask How many different phenomena can the hypothesis
explain? Other things being equal, the more it explains, the less likely
it is to be mistaken. In Chapter 3 we discussed the well-confirmed
hypothesis that human perception is constructive. As we pointed out, the
hypothesis explains a broad range of phenomena, including perceptual size
constancy, misperception of stimuli, hallucinations, pareidola, certain
UFO sightings, and more. A hypothesis that explains only one of these phenomena
(for example, the hypothesis that UFO sightings are caused by actual alien
spacecraft) would be much less impressive -- unless it had other things
in its favor like compelling evidence.

4. Simplicity. Ask Is this hypothesis the simplest explanation
for the phenomenon? Generally, the simplest hypothesis that explains the
phenomenon is the best, the one least likely to be false. Simplest
means makes the fewest assumptions. In the realm of weird things, this
is often a matter of postulating the existence of the fewest entities.
Lets say you get into your car one morning, put the key in the ignition,
and try to start the engine but find that it won't start. One hypothesis
for this phenomenon is that the car battery is dead. Another is that a
poltergeist (a mischievous spirit) has somehow caused your car not to start.
The battery hypothesis is the simplest (in addition to being testable,
able to yield predictions, and capable of explaining several phenomena)
because it doesn't require postulating the existence of any mysterious
entities. The poltergeist hypothesis, though, does postulate the existence
of an entity (as well as assuming that the entity has certain capabilities
and tendencies). Thus the criterion of simplicity shows us that the battery
hypothesis has the greater chance of being right.

5. Conservatism. Ask Is the hypothesis consistent with our well-founded
beliefs? That is, is it consistent with the empirical evidence -- with
results from trustworthy observations and scientific tests, with natural
laws, or with well-established theory? Trying to answer this question
takes you beyond merely cataloguing evidence for hypotheses to actually
assigning weight to hypotheses in light of all the available evidence.
Other things being equal, the hypothesis most consistent with the entire
corpus of our knowledge is the best bet, the one most likely to be true.

It follows that a hypothesis that flies in the face of extremely well-established
evidence must be assigned a very low probability. Say, for example, that
someone claims that yesterday thousands of cats and dogs rained down from
the sky in Texas. This strange happening is logically possible, of course,
but it conflicts with an enormous amount of human experience regarding
objects that fall from the sky. Maybe one fine day cats and dogs will indeed
tumble from the clouds and surprise us all. But based on a massive amount
of experience, we must assign a very low probability to such a possibility.

What if someone claims to have built a perpetual motion machine, a device
that, to work, must successfully circumvent one of the laws of thermodynamics.
(A perpetual motion machine is supposed to function without ever stopping
and without needing to draw on an external source of power -- it supplies
its own energy; this violates the law of conservation of mass-energy,
which says that mass-energy can't be created or destroyed.) The laws
of thermodynamics are supported by a massive amount of empirical evidence
gathered throughout centuries. There have also been numerous failed attempts
to build a perpetual motion machine. In light of such evidence, we're forced
to conclude that it's very unlikely that anyone could avoid the laws of
thermodynamics. Unless someone is able to produce good evidence showing
that it can be done, we must say that the above claim is highly improbable.

Likewise, if someone puts forth a hypothesis that conflicts with a highly
confirmed theory, the hypothesis must be regarded as improbable until good
evidence shows that the hypothesis is right and the theory wrong. Paranormal
claims then are, by definition, improbable. They conflict with what we
know, with mountains of evidence. Only good evidence to the contrary can
change this verdict.